Messages in this thread Patch in this message | | | Subject | [patch] x86, tlb: switch cr3 in leave_mm() only when needed | From | Suresh Siddha <> | Date | Thu, 22 Mar 2012 16:33:39 -0700 |
| |
From: Suresh Siddha <suresh.b.siddha@intel.com> Subject: x86, tlb: switch cr3 in leave_mm() only when needed
Currently leave_mm() unconditionally switches the cr3 to swapper_pg_dir. But there is no need to change the cr3, if we already left that mm.
intel_idle() for example calls leave_mm() on every deep c-state entry where the CPU flushes the TLB for us. Similarly flush_tlb_all() was also calling leave_mm() whenever the TLB is in LAZY state. Both these paths will be improved with this change.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> --- arch/x86/mm/tlb.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index d6c0418..ad695cc 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -61,11 +61,11 @@ static DEFINE_PER_CPU_READ_MOSTLY(int, tlb_vector_offset); */ void leave_mm(int cpu) { + struct mm_struct *active_mm = percpu_read(cpu_tlbstate.active_mm); if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK) BUG(); - cpumask_clear_cpu(cpu, - mm_cpumask(percpu_read(cpu_tlbstate.active_mm))); - load_cr3(swapper_pg_dir); + if (cpumask_test_and_clear_cpu(cpu, mm_cpumask(active_mm))) + load_cr3(swapper_pg_dir); } EXPORT_SYMBOL_GPL(leave_mm);
| |